All these run either through the dark regions proper, or through those chiaro-oscuro areas, such as Deucalionis Regio and Pyrrhae Regio, which have hitherto been thought to be amphibious, and are probably half desert. They connect on the one hand with the canals in the bright regions, and on the other with the straits between the so-called islands,—such strait-canals as Scamander, Xanthus, and the like, if we may so designate without misunderstanding what is probably not water at all.

It is interesting thus to forestall objection about a missing link by discovering that link thus early.

Before passing on to certain other phenomena connected with the canals of like significance, we may note here an obiter dictum of the irrigation theory of some slight corroborative worth; for, if a theory be correct, it will not only fit all the facts, but at times go out of its way to answer questions. Such the present one seems to do. If the seas be seas, and the canals canals, we stand confronted by the problem how to make fresh-water canals flow out of